The general procedure for placing catheters within vessels is to track a guidewire through the vessel to the desired position and advance the catheter over the guidewire. Guidewires are required because the catheters themselves do not have sufficient column strength or torqueability to be able to be tracked or steered through the vessel. See, for instance, U.S. Pat. No. 4,884,579.
In some procedures such as angioplasty using dilatation balloon catheters, it is necessary to exchange catheters to increase balloon size. It may also be necessary in some instances to replace catheters due to material fatigue. Two guidewire techniques have been employed in such instances. In one, the initial guidewire is removed and replaced with an exchange wire that is somewhat greater than double the length of the catheter. In order to avoid the need for a separate exchange wire a second technique that involves attaching an extension wire to the initial guidewire was developed.
U.S. Pats. Nos. 4,917,103 and 4,922,923 describe an extendable guidewire assembly that employs a sleeve that is connected to the proximal end of the guidewire and into which the distal end of the extension wire is inserted. The sleeve and extension are then crimped to form a permanent joint or union between the two wires.
U.S. Pat. No. 4,875,489 describes another type of extendable guidewire assembly in which one of the wires has a tapered tip and the other has an expandable sleeve into which the tip is received. A second concentric sleeve encloses the expandable sleeve to ensure a friction fit between the tapered tip and expandable sleeve.
U.S. Pat. No. 4,966,163 describes yet another kind of extendable guidewire assembly. In this assembly one of the wires carries an internally threaded sleeve and the other wire carries a threaded head, The two wires are coupled together by threading the head into the sleeve.
U.S. patent application Ser. No. 688,915, filed 19 Apr. 1991, describes an extendable guidewire assembly in which the ends of the guidewire and extension wire carry axial interlocking members and the extension wire carries a retractable sleeve which encloses the interlocked members.
Applicant is also aware of an extendable guidewire assembly design in which one of the wires carries an open-ended sleeve and the other wire has a tapered tip encircled by a helical coil. The wires are coupled by inserting the tip into the sleeve and twisting it. The twisting causes the coil to expand and form a friction fit with the interior of the sleeve. The wires are uncoupled by twisting the tapered tip wire in the reverse direction.
U.S. patent application Ser. No. 07/983,478 filed 1 Dec. 1992 describes an extendable guidewire assembly. A first polymeric sleeve allows for the connection of the guidewire and the extension wire and a second polymeric sleeve acts as a guide to focus the guidewire into the first polymeric sleeve. The application also describes a kit for use in connecting and disconnecting the guidewire assembly. The kit includes the guidewire, the extension wire, the first and second polymeric sleeves and a detachment tool.
A primary object of the present invention is to provide an extendable guidewire assembly with a guidewire and extension wire that can be easily connected and disconnected and that will not kink at the junction of the wires.